This application relates to liquid flow discharge nozzles, particularly of the type used in fire fighting. It is commonplace for such fire fighting nozzles to have some form of discharge stream pattern adjustment which will permit the discharge to be varied from a straight stream to a mist or wide fog pattern by means of a longitudinally adjustable pattern sleeve which projects beyond the discharge orifice of the nozzle into the path of the stream. The pattern forming sleeve is usually metal and has molded thereto a rubber bumper which serves both to protect the discharge end of the nozzle against damage or injury, as well as to provide a grooved or toothed surface for reflecting a portion of the discharge stream inwardly toward the center of the stream. Examples of this general type of stream-forming pattern sleeve structure are disclosed in U.S. Pat. Nos. 3,387,791; 3,540,657 and 3,784,113.
As the pattern sleeve on the nozzle is adjusted from the straight stream position to the wider fog pattern, a progressively increasing portion of the discharge stream is directed toward the teeth on the bumper. The forward or inwardly directed surfaces of these teeth are flat and are deliberately designed to reflect those portions of the stream which impinge upon it directly back into the central portion of the discharge stream.
The teeth are circumferentially spaced from each other and the non-reflected portion of the stream passes divergently upwardly of the nozzle through the passageways or spaces between the teeth.
By reason of the customary structure of fire-fighting nozzles, which include a central baffle head arrangement, the center portion of the discharge stream contains far fewer water particles than the other portions of the discharge stream. This center portion defines a low pressure area resulting from the jet stream or aspirator effect of the high velocity flow of liquid surrounding it. This central hollow core of the discharge stream is undesirable both from the standpoint of the safety of the hose handler as well as from the standpoint of effectively and efficiently extinguishing a fire.
The purpose of providing the reflecting surfaces on the bumper teeth is to attempt to get some of the water to bounce back into the central void in the discharge stream and thereby increase the water content in this hollow core of the stream. However, the major portion of the discharge stream passes between the spaced teeth and forms the "fingers" of a typical cone pattern. Only a minor proportion of the stream actually is reflected back by the fingers into the hollow central core.